Polyol blends and polyurethane prepared therefrom

ABSTRACT

A poly(oxyethylene-oxypropylene)glycol and poly(tetramethylene ether)glycol are blended together and the resulting blend and a chain extender are reacted with an organic diisocyanate under conditions which produce a thermoplastically processible polyurethane elastomer. The polyurethane elastomer can be used to advantage for making the sheath of a hydraulic hose.

This invention relates generally to poly(alkyleneether)glycols andpolyurethane elastomers prepared therefrom and, more particularly, to anovel blend of poly(ethylene oxide) poly(1,2-propylene oxide)glycol andpoly(tetramethylene ether)glycol and polyurethane elastomers preparedtherefrom.

IT HAS BEEN PROPOSED BEFORE TO PREPARE POLYURETHANE ELASTOMERS FROMPOLY(TETRAMETHYLENE ETHER)GLYCOLS IN THE Hill, U.S. Pat. No. 2,929,800and to prepare polyurethane elastomers from poly(ethylene-ether)glycolsin the Windemuth, U.S. Pat. 2,948,691 and from poly(propyleneether)glycols in the Price, U.S. Pat. No. 2,866,744. It is also proposedin U.S. Pat. No. 2,899,411 to prepare polyurethane elastomers suitablefor thermoplastic processing such as by extrusion from poly(methyleneether)glycols. While it has been proposed in various patents to preparepolyurethane elastomers suitable for extrusion of similar thermoplasticprocessing from poly(propylene ether)glycol polymers, it has been thepractice commercially to make such elastomers from poly(tetramethyleneether)glycols instead of poly(ethylene ether)glycol or poly(propyleneether)glycols because of the superior processing characteristics of theresulting polyurethane and also because of its improved hydrolyticstability and other physical characteristics. The poly(tetramethyleneether)glycols are relatively expensive, however, and cannot be used inmaking some finished products because the resulting costs of the articlewould be excessive.

It is therefore an object of this invention to provide a polyurethaneelastomer prepared from a polyol containing a poly(propyleneether)glycol and having improved tensile strength, elongation andtensile modulus which adapt it to be thermoplastically processed suchas, for example, by extrusion. Another object of the invention is toprovide a thermoplastically processible polyurethane elastomer preparedfrom a polyol containing poly(propylene ether)glycol and havingproperties which adapt it to be used instead of a polyurethane preparedfrom the more expensive poly(tetramethylene ether)glycol. A stillfurther object of the invention is to provide a method for making apolyurethane elastomer suitable for use in extrusion processes toprepare extruded elastomeric articles such as, for example, a sheath orcore tube for a hydraulic hose or the like.

The foregoing objects and others are accomplished in accordance withthis invention, generally speaking, by providing (A) a physical blend of(1) a block copolymer of ethylene oxide and 1,2-propylene oxide havingthe formula

    HO[(C.sub.2 H.sub.5 - O).sub.x (C.sub.3 H.sub.6 - O).sub.y (C.sub.2 H.sub.5 - O).sub.z ]H

wherein x and z are integers of from 0 to 22 and y is an integer of from1 to 20 and the molecular weight of the copolymer is between 500 and3000 and (2) poly(tetramethylene ether)glycol having a molecular weightof from about 500 to about 3000; (B) a substantially non-porousthermoplastically processible polyurethane elastomer prepared byreacting the blend (A) and a low molecular weight chain extender havingas its only reactive hydrogen groups primary hydroxyl groups with anorganic diisocyanate, and (C) a hydraulic hose having a core tube and/orsheath shaped by extruding the polyurethane (B). The molar ratio of (CH₂-CH₂ -O) to (C₃ H₆ -O) in the block copolymer may be from about 0.05% to95%, respectively. The block copolymer should have a primary hydroxylcontent of from about 60% to 100% by weight. The blend (A) may containfrom about 5 parts by weight to about 95 parts by weight of the ethyleneoxide tipped block copolymer (1) and the remainder poly(tetramethyleneether)glycol (2).

It has been found that a polyurethane prepared from a blend A of theblock copolymer (1) defined herein and a poly(tetramethyleneether)glycol (2) has physical characteristics which adapt it to be usedto advantage for making articles by thermoplastic processing such as,for example, extrusion, injection molding and the like with asignificant reduction in material costs where it is substituted for apolyurethane in which poly(tetramethylene ether)glycol is thepoly(alkylene ether)glycol.

The polyurethane may be prepared by reacting the blend (A) and asuitable chain extender with an organic diisocyanate under conditionswhich produce a product which can be thermoplastically processed. Suchprocesses are described by Saunders and Frisch inPolyurethanes:Chemistry and Technology, Part II pp. 376-384, publishedby Interscience Publishers, the disclosure of which is incorporatedherein by reference. Any suitable low molecular weight glycol havingonly primary hydroxyl groups such as, for example, ethylene glycol, 1,3propane glycol, 1,4-butane diol, diethylene glycol, bis-hydroxyethylether of hydroquinone, 1,5-pentane diol,bis-hydroxy ethyleneterephthalate, and mixtures thereof may be used. While any suitableorganic diisocyanate including those listed in the Frisch and Saundersbook and in U.S. Pat. No. 2,948,691 may be used, it is preferred to use4,4-diphenyl methane diisocyanate (MDI). The ratio of -NCO groups tototal -OH groups in the reaction mixture should be from about 1.07 to1.01 to 1. The molar ratio of polyols (1) and (2) to chain extendershould be from about 6.5 to 1.5 to 1.

The process for making the polyurethane involves, generally speaking,mixing the polyols (1) and (2) together in the correct proportions,heating the resulting blend to de-areate and remove moisture therefrom,mixing the resulting substantially anhydrous polyol with the chainextender, mixing the mixture of polyol and chain extender with organicdiisocyanate, pouring the resulting mixture before it solidifies over asuitable substrate and after chemical reaction has proceeded to thepoint where the coating on the substrate has solidified, heating thecoating until the product has properties which adapt it forthermoplastic processing. Preferably, the organic diisocyanate is mixedwith the polyol blend A and chain extender at a temperature of about125° F to 200° F while the polyol blend and chain extender are at atemperature of about 150° - 160° F.

It has been found that the blends of polyols contemplated by thisinvention when reacted with a suitable organic diisocyanate such as MDIconsistently produce an elastomeric polyurethane having a tensilestrength of at least about 3500 psi and an elongation at break of atleast about 300% and a modulus at 50% elongation of at least about 900psi.

The invention is further clarified and described by the followingnon-limiting examples where all parts are by weight unless otherwisespecified.

EXAMPLE 1

About 53 parts poly(oxyethylene-poly(oxypropylene)glycol having amolecular weight of about 1000 and containing between 85 and 90% byweight primary hydroxyl groups are mixed with 50 partspoly(tetramethylene ether)glycol and the resulting polyol blend isheated to about 150° F in a vacuum oven for about 2 under about 27inches vacuum until the blend is de-areated and dehydrated. About 25.2parts 1,4-butane diol are added to the mixture and about 97.8 parts MDIwhich has been heated to about 150° C are rapidly mixed with the polyolblend-1,4-butane diol mixture. After a substantially uniform mixture isobtained, the liquid reaction mixture is poured over a Teflon coatedplate and heated in an oven for about 16 hours at 150° F.

The resulting polyurethane elastomer has the following properties:

    ______________________________________                                               Tensile strength (psi)                                                                            6135                                                      50% modulus (psi)   1650                                                      elongation at                                                                 Vicat softening pt (degrees F)                                                                    292                                                ______________________________________                                    

The physical and thermal properties of this product are such that it canbe used to advantage to extrude a core tube or sheath for a hydraulichose.

EXAMPLE 2

This example is the same as Example 1 with the exception that about 27.9parts 1,4-butane diol and about 105.6 MDI are used. The physicalproperties of the elastomer are as follows:

    ______________________________________                                               Tensile (psi)       5890                                                      50% modulus (psi)   2000                                                      elongation at break %                                                                             380                                                       vicat softening pt (degrees F)                                                                    364                                                ______________________________________                                    

EXAMPLE 3

This example is the same as Example 1 except about 22.5 parts 1,4-butanediol and about 90.1 parts MDI are used. The physical properties of theelastomer are:

    ______________________________________                                               Tensile (psi)       4560                                                      50% modulus (psi)   1525                                                      elongation at break %                                                                             410                                                       Vicat softening pt (degrees F)                                                                    257                                                ______________________________________                                    

EXAMPLE 4

This example is similar to Example 1 except about 63.7 parts ofpoly(oxyethylene-oxypropylene)glycol, about 40 parts poly(tetramethyleneether)glycol, about 32.8 parts of diethylene glycol and about 97.8 partsof MDI are used.

    ______________________________________                                               Tensile (psi)                                                                 50% modulus (psi)   1205                                                      elongation at break %                                                                             425                                                       Vicat softening pt (degrees F)                                                                    187                                                ______________________________________                                    

EXAMPLE 5

This example is a comparative example and is the same as Example 1except that instead of a blend A of polyols, the polyether glycol is53.1 parts poly(oxyethylene-oxypropylene)glycol containing approximately90% primary hydroxyl groups, the chain extender is about 16.4 partsdi-ethylene glycol and about 52.8 parts MDI are used. The physicalproperties of the resulting elastomer are:

    ______________________________________                                               Tensile (psi)       5475                                                      50% modulus (psi)   630                                                       elongation at break %                                                                             425                                                       vicat softening pt (degrees F)                                                                    179                                                ______________________________________                                    

EXAMPLE 6

The example is like Example 1 except that instead of using a blend ofpolyols, only poly(oxyethylene-oxypropylene)glycol containingapproximately 90% primary hydroxy groups is used. About 106.2 parts ofthe polyol are mixed with about 25.2 parts 1,4-butane diol and about97.8 parts MDI. The elastomer has the following physical properties:

    ______________________________________                                               Tensile (psi)       2500                                                      50% modulus (psi)   1530                                                      Elongation at break %                                                                             400                                                       Durameter Shore A   95                                                        Vicat softening pt (degrees F)                                                                    244                                                ______________________________________                                    

EXAMPLE 7

This example is like Example 1 with the exception that onlypoly(tetramethylene ether)glycol is used as the polyol. The polyol has amolecular weight of about 1000. About 50 parts of the polyol are mixedwith about 10.4 parts 1,4-butane diol and about 42.5 parts MDI. Theresulting elastomer has the following properties:

    ______________________________________                                               Tensile (psi)       6000                                                      50% modulus (psi)   1500                                                      Elongation at break %                                                                             400                                                       Durameter, Shore A  95                                                        Vicat softening pt (degrees F)                                                                    270                                                ______________________________________                                    

Although the invention has been described in detail for the purposes ofillustration, it is to be understood that such detail is solely for thatpurpose and variations can be made therein by those skilled in the artwithout departing from the spirit and scope of the invention except thatit may be limited by the claims.

What is claimed is:
 1. A thermoplastically processible polyurethaneprepared by reacting an organic diisocyanate, a low molecular weightglycol chain extender having only primary hydroxyl groups and a blend offrom about 5 to about 95 parts by weight per 100 parts of a blockcopolymer of ethylene oxide and 1,2-propylene oxide having the formula

    HO[(C.sub.2 H.sub.5 - O).sub.x (C.sub.3 H.sub.6 - O).sub.y (C.sub.2 H.sub.5 - O).sub.z ]H

wherein x and z are integers of from 0 to 22 and y is an integer of from1 to 20 and the molecular weight of the copolymer is between 500 and3000 and the remainder poly(tetramethylene ether)glycol having amolecular weight of from about 500 to about 3000, said block copolymercontaining from about 60 to about 100 percent primary hydroxyl groups.2. A hydraulic hose having a sheath prepared by extrusion of thepolyurethane of claim
 1. 3. The polyurethane of claim 1 wherein theorganic diisocyanate is MDI.
 4. The polyurethane of claim 1 where thechain extender is diethylene glycol.
 5. The polyurethane of claim 1wherein the chain extender is 1,4-butane diol.
 6. The polyurethane ofclaim 1 wherein the chain extender is bis-hydroxy-ethyleneterephthalate.
 7. The polyurethane of claim 1 wherein the chain extenderis bis-hydroxy ethyl ether of hydroquinone.